1. Field of the Invention
The present invention relates to an ink jet apparatus for recording in which ink is discharged as a droplet from a discharge port of a recording head by driving energy generating means provided corresponding to the discharge port on the basis of the record information transmitted. The present invention also relates to a method of recovering in ink jet head.
Particularly, the present invention relates to an ink jet apparatus in which, in an ink jet recording method, the intensity of energy employed for discharging ink as a droplet from a discharge port (referred to as "an orifice" hereinafter) is controlled so that ink which is not discharged as a droplet is used for dummy wiping, and to a method of recovering an ink jet head.
2. Related Background Art
Recording apparatuses such as printers, copying machines, facsimiles and the like are designed so as to record images comprising dot patterns on recording materials such as paper, thin plastic plates and the like by driving the energy generating means of recording heads on the basis of the image information transmitted thereto.
Such recording apparatuses are divided into an ink jet type, a wire dot type, a thermal type, a laser beam type and the like according to various recording methods. In the ink jet type (ink jet recording apparatus) recording is performed by discharging ink (recording solution) as droplets from the discharge ports of a recording head and causing the droplets to adhere to a recording material such as paper.
The above ink jet recording apparatus has an advantage in that, since ink is discharged as small droplets, high-precision images can be recorded a% high speed.
However, the influence of the ink mist produced when ink droplets are discharged from discharge ports or when ink droplets are caused to adhere to a recording material increases with an increase in the density of discharge ports.
Namely, an increase in the number of discharge ports per unit area of the discharge port surface of a recording head results in an increase in the frequency with which the floating mist particles generated between the recording head and the recording material (a recording medium such as paper, a thin plastic plate or the like) and in the vicinity thereof adhere to a portion of the discharge port surface which is near the discharge ports of the recording head.
FIG. 1 is a schematic sectional view showing a normal state (upper side) of an ink droplet discharged and a state (lower side) of an ink droplet discharged when an ink mist particle 15 adheres to a discharge port surface 11.
In FIG. 1, when the ink mist particle 15 adheres to a portion of the discharge port surface 11 near a discharge port 6a which is provided therein and communicates with a liquid passage 6, the ink mist particle 15 causes the bending of the direction of the droplet 14 discharged from the discharge port, or, in some cases, the occurrence of a so-called sagging non-discharge phenomenon which prevents the discharge of droplets from the discharge port. This causes a deterioration in quality of the image recorded.
Particularly, when the volume of each droplet is reduced in order to obtain a high-precision image, the above-described tendency is remarkable.
Some methods have been therefore proposed for preventing or removing the adhesion of a floating ink mist particle to a discharge port surface.
Known examples of such methods include a method of providing an ink mist particle adhesion preventing member between a recording head and a recording material (Japanese Patent Laid-Open No. 54-101322), a method of providing a member for positively absorbing a mist (Japanese Patent Laid-Open No. 57-207066), a method of removing a floating ink mist particle by forming an air stream using a fan or the like (Japanese Patent Laid-Open No. 57-84857) and the like.
In addition, in order to remove unnecessary ink, including a floating ink mist particle, so as to prevent a discharge failure of ink and recover normal discharge, for example, the recovery device used in an ink jet recording apparatus (referred to as "a liquid jet recording apparatus" hereinafter) is provided with a blade made of an elastic material for cleaning a plurality of discharge ports on an ink jet head. For example, the blade is formed so as to slide on a discharge surface while moving relatively to the discharge ports for the purpose of cleaning the discharge ports and the circumference thereof.
Typical examples of the structures of such apparatuses include the following:
1) All the discharge ports of an apparatus are wiped by using a single blade. PA1 2) Each of a plurality of heads is provided with an exclusive blade. PA1 3) A member for cleaning a blade is provided in the apparatus body. PA1 1) When all the discharge port surfaces of a plurality of ink jet heads, which are provided corresponding to respective colors, are cleaned by using a single blade, the quality of an image is deteriorated by mixing of the ink colors of the heads. If wiping is performed during printing, the total printing time is increased, and thus the throughput of printing is decreased. PA1 2) When the discharge port surface of each of a plurality of ink jet heads is cleaned by using an exclusive blade, although a deterioration in quality of the image formed, which is caused by mixing of ink colors, can be prevented, the adhesion of ink to the discharge port surfaces, which is caused by wiping, causes the occurrence of a discharge failure including non-discharge or deviation in the direction of discharge of ink, thereby adversely deteriorating the discharge stability.
However, there is a problem from the technical viewpoint in that the employment of one of the above methods causes an increase in the size of a recording apparatus.
Further, since the distance between the ink jet recording head and the discharge port surface is generally as small as 2 to 3 mm, it is very difficult to provide the member for removing or preventing an ink mist particle in the portion where a high-density ink mist frequently occurs.
The above examples also have the following problems
3) The discharge stability can be further improved by providing a member for cleaning a blade in an apparatus. However, since a new member for cleaning the blade is provided in the apparatus, the cost of the apparatus is increased, and the need for the time for cleaning the blade causes a decrease in throughput of printing. In addition, the abrasion of the discharge port surfaces, which is caused by sliding of the wiping blade on the discharge port surfaces of the ink jet heads, causes discharge failure including non-discharge, deviation in the discharge direction of ink or the like, thereby adversely deteriorating the discharge stability.